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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const arr = [1,2,3,4,5];
        const arr3 =arr.concat([7,8]);
        console.log(arr3);
        // 重新申请一块空间 ，开销大
        const arr2 = JSON.parse(JSON.stringify(arr));//引用式拷贝
        arr2[0]=0;
        console.log(arr);
        console.log(arr2);
    </script>
</body>
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